Abstract
Grain-scale strain heterogeneity characteristics play a critical role in the ductile damage behavior and mechanical properties of two-phase titanium alloys. In this work, the grain-scale strain distribution, strain heterogeneity, and strain localization of titanium alloy with tri-modal microstructure (consisting of equiaxed α (αp), lamellar α (αl), and β transformed matrix (βt)) during tensile deformation were experimentally investigated. The results show that the strain probability distribution of the whole microstructure obeys normal distribution during deformation. Significant strain heterogeneities exist in each constituent (αp, αl, and βt) and the whole microstructure. At lower macro-strain, αp and αl exhibit higher average strain than those of βt and the whole of the microstructure. Meanwhile, strain heterogeneity of each constituent is small and has a negligible change. The strain heterogeneity of the whole microstructure is mainly determined by αp. At larger macro-strain, some highly deformed regions produce and their positions do not change during further deformation. As a result, the strain heterogeneity of each constituent increases fast, and the strain heterogeneity of whole microstructure is mainly related to αl in this deformation stage. On the other hand, two types of strain localization may be generated within αp and αl and at the αp/βt and αl/βt boundaries, respectively. The former type is caused by transgranular intense slip deformation and presents crystal orientation dependence. The latter type is related to the boundary sliding and presents spatial distribution dependence for αl. These strain localizations greatly determine the micro-damages, thus forming the corresponding micro-voids within αp and αl and the micro-cracks at αp/βt and αl/βt boundaries in tri-modal microstructure at larger deformation.
Highlights
Two-phase titanium alloys are widely used in medicine and aviation fields
The strain heterogeneity characteristics, strain localization mechanism, and its effect on the micro-damage were analyzed. It will deepen the understanding on grain-scale strain heterogeneity and damage behavior of titanium alloy with tri-modal microstructure
When the macro-strain reaches to macro-strain reaches to 4.7%, four highly deformed regions are formed, as indicated by arrows in
Summary
Two-phase titanium alloys are widely used in medicine and aviation fields. In the field of medical engineering, they are mainly applied in the form of orthopedic implants and surgical implants, such as the hip implants, knee joints, and substitutions of shoulder, spine, elbow, and hand. Lai et al [13] and Jafari et al [14] investigated the influence of martensite volume fraction and spatial distribution on the strain localization and damage behavior of DP steel, respectively These works suggest that the strain heterogeneities and failure mechanism of DP steel strongly depend on the morphology, content, size, and distribution of ferrite and martensite. The grain-scale strain distribution of titanium alloy with tri-modal microstructure during tensile deformation was characterized by microscopic DIC technique. The strain heterogeneity characteristics, strain localization mechanism, and its effect on the micro-damage were analyzed It will deepen the understanding on grain-scale strain heterogeneity and damage behavior of titanium alloy with tri-modal microstructure
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